title: Durability of antibody responses after receipt of the monovalent 2009 pandemic influenza A (H1N1) vaccine among HIV-infected and HIV-uninfected adults.
abstract: BACKGROUND
  Human immunodeficiency virus (HIV)-infected persons are at risk for severe influenza infections. Although vaccination against the H1N1 pandemic influenza strain is recommended, currently there are no data on the durability of post-vaccination antibody responses in this population.
  
  
  METHODS
  HIV-infected and HIV-uninfected adults (18-50 years old) received a single dose of monovalent 2009 influenza A (H1N1) vaccine (strain A/California/7/2009H1N1). Antibody levels to the 2009 H1N1 pandemic strain were determined at day 0, day 28, and 6 months by hemagglutination-inhibition assay. A seroprotective response was a post-vaccination titer of ≥1:40 among those with a pre-vaccination level of ≤1:10. Geometric mean titers (GMT) and factors associated with higher levels were also evaluated.
  
  
  RESULTS
  We studied 127 participants with a median age of 35 (interquartile range (IQR) 28, 42) years. Among the HIV-infected arm (n=63), the median CD4 count was 595 (IQR 476, 819)cells/mm(3) and 83% were receiving HAART. Thirty-five percent of all participants had a pre-vaccination level of >1:10. HIV-infected compared to HIV-uninfected adults were less likely to generate a seroprotective response at day 28 (54% vs. 75%, adjusted OR 0.23, p=0.021) or have a durable response at 6 months post-vaccination (28% vs. 56%, adjusted OR 0.19, p=0.005). Additionally, although pre-vaccination GMT were similar in both arms (median 7 vs. 8, p=0.11), the GMT at 6 months was significantly lower among HIV-infected versus HIV-uninfected adults (median 20 vs. 113, p=0.003). Among HIV-infected persons, younger age (p=0.035) and receipt of HAART (p=0.028) were associated with higher GMTs at 6 months.
  
  
  CONCLUSIONS
  Despite vaccination, most HIV-infected adults do not generate durable seroprotective antibody responses to the 2009 influenza A (H1N1) virus, and hence may remain vulnerable to infection. In addition to HAART use, more immunogenic vaccines are likely needed for improving protection against influenza in this population.
authors.affiliation: Infectious Disease Clinical Research Program, Uniformed Services University of the Health Sciences, Bethesda, MD, USA. nancy.crum@med.navy.mil
authors.forename: Nancy F
authors.initials: NF
authors.lastname: Crum-Cianflone
authors.forename: Erik
authors.initials: E
authors.lastname: Iverson
authors.forename: Gabriel
authors.initials: G
authors.lastname: Defang
authors.forename: Patrick J
authors.initials: PJ
authors.lastname: Blair
authors.forename: Lynn E
authors.initials: LE
authors.lastname: Eberly
authors.forename: Jason
authors.initials: J
authors.lastname: Maguire
authors.forename: Anuradha
authors.initials: A
authors.lastname: Ganesan
authors.forename: Dennis
authors.initials: D
authors.lastname: Faix
authors.forename: Christopher
authors.initials: C
authors.lastname: Duplessis
authors.forename: Tahaniyat
authors.initials: T
authors.lastname: Lalani
authors.forename: Timothy
authors.initials: T
authors.lastname: Whitman
authors.forename: Carolyn
authors.initials: C
authors.lastname: Brandt
authors.forename: Grace
authors.initials: G
authors.lastname: Macalino
authors.forename: Eugene V
authors.initials: EV
authors.lastname: Millar
authors.forename: Timothy
authors.initials: T
authors.lastname: Burgess
mesh_terms: D000293:Adolescent; D000328:Adult; D000914:Antibodies, Viral / Q000097:blood*; D005260:Female; D015658:HIV Infections / Q000276:immunology*; D006385:Hemagglutination Inhibition Tests; D006801:Humans; D053118:Influenza A Virus, H1N1 Subtype / Q000276:immunology*; D007252:Influenza Vaccines / Q000008:administration & dosage / Q000276:immunology*; D007251:Influenza, Human / Q000276:immunology* / Q000517:prevention & control; D008297:Male; D008875:Middle Aged; D013997:Time Factors; D055815:Young Adult
chemical_list: D000914:Antibodies, Viral; D007252:Influenza Vaccines